This application is based on Patent Application No. 2001-232919 filed Jul. 31, 2001 in Japan, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The invention relates to inkjet printing apparatuses and methods for detecting the amount of remaining ink in the inkjet printing apparatuses, and particularly, to a method for detecting remaining ink level.
2. Description of the Related Art
Some of the conventional printing apparatuses such as inkjet printers, which use ink for printing, execute detecting of the remaining ink level so as to stop a printing operation or to provide an indication urging users to exchange the ink tank, when ink has run out or the ink level has become as low as to cause problems in printing. As methods for detecting ink levels, there have been proposed a variety of methods. For example, sensors are known as those directly detect the presence/absence of ink or a remaining level of ink, such as optical sensors utilizing a light interception by ink, electric sensors utilizing electric resistance change due to the presence/absence of ink, and mechanical sensors utilizing a lever that moves together with the ups and downs of the ink level. There is also a method that accumulates data about ink consumption during operations such as printing and recovering and then estimates the remaining level based on the accumulated data.
It is possible to check if the remaining ink level has fallen below a predetermined level by the use of such optical, electric and mechanical sensors of relatively simple structure and low cost. These sensors, however, have such disadvantages that the control process becomes complex and additional cost arises from detection components when estimating the remaining ink level in detailed scales.
On the other hand, the method for estimating the remaining ink level based on the accumulated data of ink consumption has the advantage of being capable of estimating the remaining ink level in detailed scales at relatively low cost. However, there are variations in the estimate of ink consumption due to variations in the ejection quantity and performance of the recovering mechanism. In addition, the capacity of the ink tank and the amount of filled ink may also vary. As a result, the estimated remaining ink level may significantly differ from the actual ink level. Further, it is also necessary to introduce some margin in the estimate of ink levels, taking such errors into account. Then, in turn, such a problem arises that the printing is stopped or the indication of ink-out is issued although the ink tank still has ink.
The object of the present invention is to provide an inkjet printing apparatus and a remaining ink level detection method that detect the remaining ink level precisely in detailed scales with a low-cost and simple structure using a sensor.
In the first aspect of the present invention, there is provided a remaining amount detecting method of detecting an amount of remaining ink in an ink reservoir, comprising the steps of:
providing sensing means for detecting whether the amount of remaining ink in the reservoir is below a predetermined level or not, detection state memory means for storing a state that the sensing means detects that the amount of remaining ink is below the predetermined level or a state that the amount of remaining ink is not below the predetermined level, and calculation means for calculating ink consumption in the ink reservoir based on an operation of means using the ink; and
determining the amount of remaining ink on the predetermined level basis by using an ink consumption calculated by the calculation means and a threshold value as the ink consumption that is calculated by the calculation means and then supposed to reach the predetermined level for the sensing means;
wherein when the sensing means detects that the amount is below the predetermined level and the detection state stored in the detection state memory means is that the amount of remaining ink is not below the predetermined level, the ink consumption calculated by the calculation means is made a content of the threshold value.
In the second aspect of the present invention, there is provided an inkjet printing apparatus using a printing head for ejecting ink and an ink reservoir for storing ink supplied to the printing head to perform printing on a printing medium, and detecting an amount of remaining ink in the ink reservoir, the apparatus comprising:
sensing means for detecting whether the amount of remaining ink in the reservoir is below a predetermined level or not;
detection state memory means for storing a state that the sensing means detects that the amount of remaining ink is below the predetermined level or a state that the amount of remaining ink is not below the predetermined level;
calculation means for calculating ink consumption in the ink reservoir based on an operation of means using the ink; and
determining the amount of remaining ink on the predetermined level basis by using an ink consumption calculated by the calculation means and a threshold value as the ink consumption that is calculated by the calculation means and then supposed to reach the predetermined level for the sensing means;
wherein when the sensing means detects that the amount is below the predetermined level and the detection state stored in the detection state memory means is that the amount of remaining ink is not below the predetermined level, the ink consumption calculated by the calculation means is made a content of the threshold value.
According to the above configuration, in determining a remaining amount of ink, when the sensing means detects that the remaining amount is equal to or less than a predetermined level and the state stored in the detection condition memory means indicates a state that the remaining amount is not equal to or not less than the predetermined level, the ink consumption calculated by the calculation means is made the threshold value. Thereby, thus obtained threshold value is used for a next determining process of the amount of remaining ink and therefore it is possible to correct the threshold value for determining the amount of remaining ink to be the value at the time that the sensing means detects a change from a state that the remaining amount is more than the predetermined level to a state that the remaining amount is equal to or less than the predetermined level.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.